1. Field of the Invention
The present invention relates to a headstock guide unit for a machine tool where a carriage with a tool post mounted thereon is disposed on a fixed bed on one side thereof that is closer to an operator while a headstock for loading a workpiece thereon is provided on the other side of the fixed bed farther from the operator.
2. Discussion of the Related Art
Conventionally a mass-production type machine tool (such as a Numerically Controlled lathe also called an NC lathe) has carriages with a tool post mounted on each carriage are provided on the left and right sides of the front side (nearer side to the operator) of the fixed bed. The carriages are movable in X- and Z-axis directions, respectively, while a headstock is disposed on the side farther from the operator between the two tool posts.
With this type of NC lathe, a workpiece is mounted on the spindle of the headstock. The workpiece is then subjected to a specified cutting process by moving the left-and-right carriages and the tool post relative to each other while rotationally driving the workpiece.
With this conventional machine tool, because the headstock is fixedly disposed on the rear side of the left-and-right tool posts, the task of replacing the workpiece of the spindle would inevitably be performed deep in the side of the fixed bed. This results in a problem of poor replacement workability.
Also in this conventional machine tool, there are some cases where the chips generated by the workpiece machining are discharged on the side closer to the operator. In such a case, the chips are more likely to interfere with the workpiece loading/unloading tasks, further lowering the workability of the replacement tasks.
In this connection, from the viewpoint of enabling an easy replacement of the workpiece, the present inventors have developed a machine tool which comprises a headstock disposed on a headstock base, the headstock base being movable between a workpiece machining position on one side (farther from the operator) and a workpiece loading/unloading position on the other side (closer to the operator), and a chip collecting space is provided at a location of the fixed bed corresponding to the workpiece loading/unloading position.
With this machine tool, it is possible to perform the workpiece loading/unloading replacement tasks in proximity to the operator on the front side of the fixed bed. Additionally, since the chips generated by the workpiece machining operations drop into the chip collecting space of the fixed bed, it is possible to prevent these chips from interfering with the workpiece loading/unloading tasks.
When a chip collecting space is formed in a location of the fixed bed corresponding to the workpiece loading/unloading position, the headstock is supported on one side by the headstock base at the workpiece loading/unloading position. This ensures support rigidity and support strength for the headstock in the workpiece loading/unloading position.
The present invention has been accomplished in view of these conventional devices.
An object of the present invention is to provide a headstock guide unit for a machine tool that allows the workpiece loading/unloading work to be easily achieved and that allows support strength and support rigidity during its support of the headstock in the workpiece loading/unloading position to be ensured.
In order to achieve the above and other objects of the invention, there is provided a machine tool that comprises a fixed bed; a carriage with a tool post mounted thereon is provided on the fixed bed on one side; and a headstock is provided on another side so that the headstock is connected to a headstock base and is movable between a workpiece machining position for machining a workpiece and a workpiece loading/unloading position for loading or unloading a workpiece. The tool also includes a chip collecting space disposed in a cut out portion of the fixed bed adjacent to the workpiece loading/unloading position and a headstock guide unit comprising a guide support mechanism for supporting a front portion of the headstock base by the fixed bed when the headstock base is positioned at the workpiece machining position, and for supporting a rear portion of the headstock base by the fixed bed when the headstock base is positioned at the workpiece loading/unloading position.
In a second aspect of the invention, the headstock guide unit for a machine tool as described in the first aspect has a guide support mechanism that comprises rails disposed so as to extend along left-and-right edge portions of the chip collecting space of the fixed bed; and guides disposed on the headstock base and slidably engaged with the rails.
In a third aspect of the invention, in the headstock guide unit for a machine tool as described in the first aspect has a guide support mechanism that includes a first cam follower disposed on the fixed bed in rolling contact with a front lower surface of the headstock base; and a second cam follower disposed at a rear portion of the fixed bed, rearwardly of the first cam follower, in rolling contact with a rear upper surface of the headstock base.
With the headstock guide unit according to the present invention, since the headstock is fixed to the headstock base and since the headstock base movable between the workpiece machining position on one side and the workpiece loading/unloading position on the other side, the task of loading and unloading the workpiece can be carried out in a location in proximity to the operator on the front side of the fixed bed. This allows the workpiece loading/unloading workability to be improved.
Also in this invention, since the chip collecting space is provided in a portion of the fixed bed corresponding to the workpiece loading/unloading position, the chips generated by the workpiece machining operations drop into the chip collecting space of the fixed bed. Thus, it is possible to prevent the chips from interfering with the workpiece loading/unloading tasks, and therefore the workability is improved.
Furthermore, in the present invention, since the headstock guide unit further comprises a guide support mechanism for supporting a front portion of the headstock base by the fixed bed when the headstock base is positioned at the workpiece machining position, and for supporting a rear portion of the headstock base by the fixed bed in the workpiece loading/unloading position, support rigidity and support strength for the headstock in the workpiece machining position can be ensured. Moreover the headstock can be moved to the workpiece loading/unloading position without any obstacles.
Also, according to the second aspect of the invention, since the guide support mechanism comprises rails disposed on left-and-right edge portions of the chip collecting space of the fixed bed, and guides disposed on the headstock base and slidably engaged with the rails, the headstock base can be securely supported while sliding along the guides and the rails even when the headstock base overhangs the workpiece during the loading/unloading process.
Also, according to the third aspect of the invention, since the guide support mechanism comprises a first cam follower in rolling contact with a front lower surface of the headstock base and a second cam follower in rolling contact with a rear upper surface of the headstock base, the headstock base can be supported so as to be movable between the workpiece loading/unloading position and the workpiece machining position at a low cost and with a simple construction.